Problems with Varnishing Epoxy

We had received a few reports of problems with varnishing epoxy that we were unable to explain.

Thanks to Malcolm Whitehead who told us about Amine blush.

Essentially when epoxy dries a wax like film can be left on the surface which can interfere with the varnish unless removed. The film is water soluble.

This web page explains more about the problem and how to solve it.

www.yachtpaint.com/usa/diy/ask-the-experts/what-is-amine-blush.aspx

We have also received reports about Le Tonkinois not drying on some epoxy.

One customer used epoxy on a teak rudder. He confirmed the epoxy was the correct mixture and dried perfectly. He had sanded it back and then varnished. The rudder was in a dry heated workshop and it was still not dry after 10 days, leaving patches all over of very tacky varnish.

Le Tonkinois applied over epoxy is not usually a problem and tests revealed the varnish dried normally on plain timber.

Subsequent investigations have localised the non drying problem to West System epoxy so we do not recommend using Le Tonkinois over West System epoxies.

An experienced boat builder also told us that applying epoxy to teak was "a recipe for disaster."

Unless the teak is thoroughly scrubbed with something like acetone to remove completely the natural oil in the wood it may contaminate the epoxy. Varnish applied over this has no chance of surviving for a reasonable time.

Even if this contamination does not happen the grip between the epoxy and the teak is not very strong, leading to a tendency to separate at the edges or at sites of damage.